Research and application of roll bending method for welded pipe with large length and small diameter to thickness ratio

Because of the inefficiency of the existing production process for large diameter longitudinal submerged arc welded (LSAW) pipe, a roll bending process is proposed, but it is difficult to control the pipe straightness with large length and small diameter to thickness (D/T) ratio. A method of deflection compensation with reverse bending top roll is proposed to solve the problem. The mechanical model of the roll bending process is established, and the forces on the plate and the roll, the deflection of the top roll and the torque are analyzed systematically. A set of roll bending machines was designed and developed, and the process parameters of different specifications of products were tested. The results show that the straightness of the pipe is less than 0.1 % of full length, and the error between theoretical analysis and test data is less than 15 %. The theoretical analysis method can be used to direct the production.